Neonatal thyroxine treatment enhances classical conditioning in the infant rat

Neonatal rats injected with either thyroxine (T₄) or vehicle (NaOH) on postnatal Days 1, 2, and 3 were given classical-conditioning pairings of an odor with footshock when 7, 9, or 11 days of age. In accord with the conventional acceleration of other indices of maturation following the T₄ treatment, 24-hr retention of the conditioned odor aversion was substantially enhanced among the 11 day-old rats given the earlier T₄ treatment. This effect was marginally significant among 9-day olds but not among 7-day olds.     

The role of cytochrome P-450 forms in 2-aminoanthracene and benz[alpha]pyrene mutagenesis.

The role of four forms of cytochrome P-450 from rabbit liver in the metabolic activation of two suspected carcinogens, 2-aminoanthracene and benz[α]pyrene, was investigated with a S. typhimurium tester strain, TA 98. Each of the forms, 2,3,4 and 6 was reconstituted with NADPH-cytochrome P-450 reductase and lipid, and assay conditions were established such that the cytochrome P-450 concentration was rate-limiting. Under these conditions, cytochrome P-450 form 4, but not the other forms, converted 2-aminoanthracene into a potent mutagen. In contrast, form 6 was the only form which metabolized benz[α]pyrene to a mutagen. These results indicate that specific cytochrome P-450 forms preferentially activate particular mutagens.     

Molecular changes in cell surface membranes resulting from trypsinization of sarcoma 180 tumor cells

Sarcoma-180 tumor cells in culture or grown as an ascites form in the CD-1 mouse have been subjected to mild trypsinization procedures in order to study morphological and molecular changes resulting from proteolysis. The cells attached to a substratum become rounded within 20 min and most undergo cell division, but they do not detach from the substratum. Removal of trypsin permits the cells to go back to their original spindle shape over an 8–20 h period.Surface membranes were isolated from trypsinized ascites and cultured cells and subjected to dodecyl sulfate-acrylamide gel electrophoresis. Both cell types showed the same two kinds of changes in electrophoretic patterns. First, there was a loss of glycoproteins from both cell types, even though they show different complements of cell surface glycoproteins. Second, there is a loss of high molecular weight polypeptides, which have previously been suggested to play a role in membrane stabilization and cell shape. These results further implicate these polypeptides in the control of cell morphology and offer circumstantial evidence for transmembrane interactions of surface glycoproteins with the high molecular weight polypeptides as a factor in controlling cell morphology.     

Improved histological localization of GABA-transaminase activity in rat cerebellar cortex after aldehyde fixation

Summary A method for the chemical fixation of the enzyme GABA-transaminase in nervous tissue is described. It is shown that after perfusion with a formaldehyde/glutaraldehyde fixative, activity of the enzyme in cerebellar cortex is demonstrable whilst cellular morphology is preserved. Results from the improved technique have shown new sites of GABA-transaminase activity in cerebellar cortex. In view of these results a special function for glial cells in this area of brain has been suggested.     

Follow-up study of small-for-dates babies.

A group of small-for-dates full-term babies whose intra-uterine growth was followed by serial ultrasonic cephalometry were examined at a mean age of 4 years. Those children whose skull growth had begun to slow in utero before 34 weeks'' menstrual age were more likely to have a height and weight less than the 10th centile. When the onset of growth failure had occurred before 26 weeks there was a lower developmental quotient at follow-up using the Griffiths extended scales. Prolonged slow growth in utero therefore seems to be followed by slow growth and development after birth.